console.log('Boolean(undefined):  ' + Boolean(undefined));
console.log('Boolean(false):  ' + Boolean(false));
console.log('Boolean(0):  ' + Boolean(0));
console.log('+Boolean(1):' + Boolean(1));
console.log('Boolean(-1):' + Boolean(-1));
console.log('Boolean(""):' + Boolean(""));
console.log('Boolean(\'\'):' + Boolean(''));
var user1 = {}
var user2
console.log('Boolean(user1):' + Boolean(user1));
console.log('Boolean(user2):' + Boolean(user2));
console.log('Boolean(\'false\'):' + Boolean('false'));
console.log("-----------string------------");
console.log('String(false)' + String(false));
console.log("----------- ==or===  ------------");

console.log('\\n  123  \\t' === '123');
var str = "[1,2,3,5]";
console.log(JSON.parse(str) instanceof Array)
